As known, civil or military modern airplanes are provided, for safety reasons, with such an installation for detecting and displaying breakdowns, while allowing to monitor the operation of the functional systems of the airplane related, for example, to hydraulics, air management, pressure in the cockpit, fuel, landing gear, electricity, etc., and to warn the pilot(s) should a functional system dysfunction occurs.
An installation of such a type mainly comprises:                an general alarm system (referred to in the aeronautic field as FWS for Flight Warning System), connected to said functional systems and able to indicate the breakdowns detected on at least one display screen located substantially in front of the pilot, on the instrument panel of the cockpit; and        auxiliary alarm detection means directly originated from said functional systems, independently from said general system, and able to indicate said breakdowns being detected to warning elements located at least in part at the level of the ceiling of said cockpit, substantially above said pilot.        
In such an installation, the general alarm system centralizes and monitors the set of information (parameters, etc.) transmitted by the functional systems of the airplane and indicates, on the display screen of the instrument panel, the alarms should a breakdown of a functional system of the airplane be detected. Thus, when such a breakdown is shown, the general system FWS displays on the display screen, in the form of a page, the procedure that the crew should implement in order to process the breakdown being detected and limit, or even delete, the effects thereof. The general system FWS further communicates to the display screen the page(s) relating to the defective functional system, being displayed in parallel to that relating to the alarm. Such information allows the crew to better seize the breakdown and the associated procedure for solving it.
Any information on the operation of such functional systems is thus centralized on the display screen, in front of the pilot's or pilots' eyes.
The auxiliary alarm detection means are another source of information on the operation of the functional systems of the airplane, being independent from the general system FWS, allowing to improve the coverage of alarms and thus safety, and to prevent the non-detection of a breakdown by the general alarm system. This relates, in particular, to the most critical breakdowns such as a fire, etc. The warning elements, such as warning lights, indicators, or others, of the auxiliary means originated from the functional systems, are located at the ceiling of the cockpit, as well as on screens of the instrument panel, for example, on the synopses of the system pages, and indicates, with a light and/or sound, the breakdowns being detected.
Thus, these are detected and indicated both by the general system FWS and by the auxiliary detection means.
Furthermore, it is known that, during night tactical operations (low altitude flight, dropping on flight, etc.), pilots of military airplanes use night vision binoculars. Thus, when they are bearing such binoculars, the vision field of the pilots becomes reduced and is limited to the instrument panel of the cockpit and to the external vision, through the windscreen. Thereby, the ceiling of the cockpit and the different warning elements it comprises, are no longer visible directly to the pilot(s). Thus, they have not any longer a direct vision of the warning elements of the independent auxiliary detection means. Consequently, when the general system does not detect a breakdown of a functional system of the airplane, so that nothing is displayed on the display screen of the instrument panel, the crew bearing the night vision binoculars does not see the then active warning elements located at the ceiling and thus risks not to be informed about the breakdown and not to apply the associated procedure.
Such a problem can also occur during the day in specific military phases such as dropping, for example, when the crew has a very large workload or is already facing a technical dysfunction, so that they forget to look at the <<ceiling>> indicators.